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High glycemic (GI) diets may increase the risk of age-related macular degeneration
New research shows an association between diets high in glycemic index and an increased risk of age-related macular degeneration (AMD), the number one cause of adult blindness.
The number one cause of irreversible blindness in adults is age-related macular degeneration (AMD), which seems to share several carbohydrate-related risk factors with diabetes-related diseases, including retinopathy and cardiovascular disease (CVD). In a new study published in the American Journal of Clinical Nutrition, researchers tested the theory that dietary glycemic index (GI), which has been associated with the risk of diabetes and CVD, may also increase the risk and severity of AMD in elderly populations. Over 4000 participants aged 55-80 years participated in the research and were assigned to groups according to several physical eye characteristics related to AMD. Compared with the eyes in those with the lowest GI diets, eyes in the high GI subjects had significantly higher risk of AMD progression and severity. There was a 49% increase in the risk of advanced AMD for persons who ate a diet higher than average in GI. Researchers noted that the results indicated that 20% of all AMD cases in the study would have been eliminated if the participants consumed diets with a GI below the average. The association between dietary GI and AMD suggests that reducing the dietary GI may provide one way to reduce the risk of AMD in adults.
American Journal of Clinical Nutrition, Vol. 86, No. 1, 180-188, July 2007 |
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High antioxidant levels are associated with a reduced risk of periodontitis.
Periodontitis is an inflammatory disease that affects the supporting tissues of the teeth and is associated with an increased risk of stroke, type-2 diabetes, and heart disease. A new study reveals that increased serum antioxidant concentrations are associated with a reduced risk of periodontitis, even in people who have never smoked.
Periodontitis is an inflammatory condition of the tissue surrounding the teeth which has been linked with an increased risk of stroke, type-2 diabetes, and heart disease. A new report published in the Journal of Nutrition revealed that higher serum antioxidant levels are associated with a reduction in the risk of periodontitis.
The current research examined data from 11,480 participants in the Third National Health and Nutrition Examination Survey (NHANES III), for whom periodontal measurements and serum levels of several antioxidants had been recorded. These antioxidants included alpha-carotene, beta-carotene, selenium, lutein, beta-cryptoxanthin, vitamins A, C and E, and total antioxidant levels.
Mild periodentitis was found in 14% of the subjects and 5% had severe disease. Higher vitamin C and total antioxidant levels were associated with a lower incidence of periodontitis, especially with severe disease. Individuals whose vitamin C levels were in the top 20% of participants had a 39% lower risk of periodontitis than participants with the lowest intakes. For subjects who had never smoked, those with the highest intake of vitamin C experienced only half the risk of periodontitis compared to those with the lowest vitamin C levels.
Vitamin C has a role in collagen synthesis and maintenance of connective tissue, which may explain its benefit in protecting against periodontitis. In addition, it is known as a potent antioxidant that may also help reduce inflammation.
Journal of Nutrition Vol. 137, 657-664, March 2007. |
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NEW YORK (Reuters Health) - Chemicals found in grape seeds may help ward of skin cancer due to regular exposure to the sun, according to the results of an animal
study reported Sunday in Chicago at the 223rd annual meeting of the American Chemical
Society.
Researchers from the University of Alabama, Birmingham exposed hairless mice to
ultraviolet-light. Some of the mice they fed a standard diet supplemented with grape
seed proanthocyanidins, or GSPs, while control mice were fed a standard diet without
this supplement.
Dietary supplementation with GSPs inhibited light-induced carcinogenesis, study chief
Dr. Santosh K. Katiyar told the conference.
Mice supplemented with GSPs had up to 65 fewer tumors than control mice did.
Moreover, the tumors seen in GSP-supplemented mice were up to 78 percent smaller than
those seen in the control mice.
"It suggests that regular consumptions of GSPs as a dietary supplement may be
beneficial for the prevention of skin cancers," Katiyar said in a written statement.
GSPs appear to inhibit suppression of the immune system caused by ultraviolet light.
This is "an important characteristic of GSPs. which has not been reported by several
other dietary botanical agents," Katiyar noted.
GSPs have antioxidant activity, and UV-induced oxidative stress has been linked to
the induction of skin cancers.
Over exposure to sunlight accounts for more than one million new cases of melanoma
and non-melanoma skin cancers each year in the United States. Effective preventive
agents and strategies that can reduce or control the risk of UV-induced skin cancer
is required to address this "pressing public health issue," Katiyar said.
Based on the current findings, studies of GSPs for the prevention of skin cancers in
humans are warranted, the Birmingham team concludes. Back to Contents Back to home page |
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High Glycemic Index Diets Increase the Risk of Chronic Degenerative Disease Long-term consumption of high-glycemic foods may increase oxidative stress and the risk of chronic degenerative diseases. Leading U.S. researchers recently concluded that a low-GI diet, not a low carbohydrate diet, appears to be beneficial in reducing the production of free radicals and oxidative stress. Glycemic index (GI) is a measure of the rate that the carbohydrates in a food or meal are digested and appear in the blood as glucose (sugar). Glycemic load is a way of measuring the total carbohydrates in a meal or diet with a mathematical adjustment for GI. These measurements can be used to simultaneously describe the quality (glycemic index) and quantity of carbohydrate in a meal or diet. Recent data suggest that the sudden rise in blood sugar associated with a high glycemic load may increase free radical production and the risk of oxidative damage. This increased production has been implicated in many disease processes including chronic heart disease, accelerated aging, and type 2 diabetes. Investigators from several leading U.S. institutions recently investigated whether a diet with a high GI or GL is associated with greater oxidative stress by taking specific measurements in nearly 300 healthy adults. Participants with a higher GI and GL diet were found to exhibit increases in oxidative stress when compared to those eating a diet lower in glycemic index and load. Researchers concluded that chronic consumption of high-GI foods may lead to chronically high oxidative stress, increasing the risk for several degenerative diseases. A low-GI diet, not a low carbohydrate diet, appears to be beneficial in reducing oxidative stress. American Journal of Clinical Nutrition, Vol. 84, No. 1, 70-76, July 2006. Back to Contents Back to home page |
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Magnesium intake increases bone mineral density and may reduce the risk of osteoporosis A study published in the Journal of the American Geriatric Society has shown that dietary intake of magnesium is associated with an increase in bone mineral density in older men and women. The study included 2,038 men and women aged 70-79 that were enrolled in the Health, Aging and Body Composition Study. Food frequency questionnaires were used to assess magnesium intakes and document any medications. The data also accounted for variations in age, body mass index (BMI), smoking status, alcohol use, physical activity, estrogen use, and supplemental calcium and vitamin D. Higher magnesium intake through diet and supplements was positively associated with total - body bone mineral density (BMD) in older white men and women. For every 100 mg per day increase in magnesium, there was an approximate 2 per cent increase in whole-body BMD. The results have important implications since osteoporosis currently affects over 10 million adults in the U.S. alone, with another 34 million suspected to have low bone mass. In addition, earlier dietary surveys have consistently shown that a large portion of adults do not meet the RDA for magnesium. Journal of the American Geriatrics Society November 2005, Vol 53, No 11, pp 1875-1880 Back to Contents Back to home page |
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Free Radicals and Antioxidants Free radicals are atoms or molecules with unpaired electrons. Once formed, these highly reactive radicals may cause damage to cells, organelles, and DNA. Antioxidants are molecules that can safely interact with free radicals and terminate their reactive behavior before vital cellular components are harmed. The body cannot manufacture many antioxidants (including micronutrients like vitamin C), so they must be supplied by the diet. Free radicals (pro-oxidants) are atoms or molecules with unpaired electrons. These highly reactive substances can be formed in a number of ways, and once formed they may use their reactivity to damage important cellular components - such as the cell membrane - or macromolecules like DNA. This damage can lead to mutation, impaired function, and even cell death. To minimize potential damage from free radicals, the body utilizes a defense system of antioxidants. Antioxidants are molecules that can safely interact with free radicals and terminate their reactivity before vital cellular components are damaged. Although there are several enzyme systems within the body that scavenge free radicals, the principle micronutrient (vitamin/mineral) antioxidants are vitamin E, beta-carotene, vitamin C, and selenium. The body cannot manufacture these micronutrients, so they must be acquired by diet. In addition, there are many plant-derived nutrients (phytonutrients) that can act as powerful antioxidants in the human body. It is impossible to completely avoid damage from free radicals. Free radicals arise from sources both inside (endogenous) and outside (exogenous) our bodies. Oxidants that develop from processes within our bodies form as a result of normal breathing, metabolism, and inflammation. Exogenous free radicals form from environmental factors such as pollution, sunlight, strenuous exercise, smoking, and alcohol. Unfortunately, no antioxidant system is perfect, so cells and DNA damaged by oxidation accumulate as we age. Plentiful intakes of antioxidants have been associated with reduced risk of some chronic diseases, in the same way that generous intakes of fruits, vegetables and grains have been associated with similar health benefits. There are many known health benefits of antioxidant intake. Some scientific examples include the following: Cancer -People with high beta-carotene intakes have about one-third the cancer risk as people with low beta-carotene intakes. (Peto R. Cancer Surveys 1983;2:327-340.) -People with higher intakes of vitamin C have about half the risk for many types of cancer when compared to people with low vitamin C intakes. (Block G. Am J Clin Nutr 1991;53:270S-282S.) -People with low intakes of several antioxidants have more DNA damage than people with generous intakes. (Ames BN. Metat Res 2001;475:7-20.) -People with the highest intakes of vitamin C, E, and beta-carotene have a significantly lower risk of lung cancer. (Yong LC et al. Am J Epidemiol 1997;146:231-43.) -Men who took vitamin E supplements for 10 years or more had a 30% lower risk of bladder cancer. (Michaud DS et al. Am J Epidemiol 2000;152:1145-53.) -There are over 66 studies showing cancer-prevention activity of green tea, black tea, and their constituents. These include cancer reduction in the skin, lung, oral cavity, esophagus, stomach, liver, pancreas, bladder, small intestine, colon and prostate. (Lambert JD et al. Am J Clin Nutr 2005;81:284S-291S.) Heart Disease -Elderly people who took both vitamin C and vitamin E supplements had a decreased risk of death from heart disease as well as overall mortality. (Losonczy KG, Harris TB, Havlik RJ. Am J Clin Nutr 1996;64:190-196.) -Men who took vitamin supplements had a 70% lower risk of dying from heart disease and a 50% lower risk of heart attack. (Meyer F, Bairati I, Dagenasis GR. Can J Cardiol 1996;12:930-934.) -In the Nurses' Health Study involving over 87,000 women, there was a 41% reduction in risk of heart disease for those who took vitamin E for more than two years. (Stampfer MJ, Hennekens CH, Manson JE, et al. New Engl J Med 1993;328:1444-1449.) -In the Nurses' Health Study, vitamin C supplements were also related to a lower risk of heart disease. (Osganian SK et al. J Am Coll Cardiol 2003;42:246-52.) -In the Health Professionals Follow-Up Study involving almost 40,000 men, there was a 37% reduction in risk of heart disease in men who took vitamin E for more than two years. The average intake in the lowest risk group was 400 IU per day. (Rimm EB, Stampfer MJ. Ascherio A, et al. New Engl J Med 1993;328:1450-1456.) -To date, 17 human group studies have been published on flavonoid intake and the risk of coronary artery disease and stroke. Positive studies have shown reduction in mortality risk of up to 65%. (Arts ICW and Hollman PCH. Am J Clin Nutr 2005;81:317S-325S.) -The largest and longest study to date, done as part of the Harvard-based Nurses' Health Study and Health Professionals Follow-up Study, included almost 110,000 men and women whose health and dietary habits were followed for 14 years. The higher the average daily intake of fruits and vegetables, the lower the chances of developing cardiovascular disease. Compared with those in the lowest category of fruit and vegetable intake (less than 1.5 servings a day), those who averaged 8 or more servings a day were 30% less likely to have had a heart attack or stroke. (Joshipura KJ, et al. Ann Intern Med 2001 Jun 19;134(12):1106-14.) Other Chronic diseases -Several long-term studies have shown a reduced risk of cataracts in those who have taken vitamin C and/or vitamin E supplements for more than 10 years. (Jacques PF et al. Arch Ophthalmol 2001;119:1009-19.) -The Age-Related Eye Disease Study (AREDS) at NIH found that daily supplementation with antioxidants, zinc, and copper delayed progression of age-related macular degeneration. (AREDS report no. 8. Arch Ophthalmol 2001;119:1417-36.) -Research has shown a significant relationship between flavonoid intakes and the occurrence of asthma. (Knekt P et al. Am J Clin Nutr 2002;76:560-8.) -Other research suggests antioxidants may help support lung function and protect the lungs from oxidative damage. (Schunemann HJ et al. Am J Respir Crit Care Med 2001;163:1246-55.) -In a study on Alzheimer's disease, high levels of vitamin E delayed progression of the disease. (Sano M et al. N Engl J Med 1997;336:1216-22.) Back to Contents Back to home page |